System for adjusting the tension of the upper thread in a sewing machine

ABSTRACT

A system for adjusting the tensile stress to which the upper thread of the machine is subjected by means of a spring engaging an arrangement including a spindle carrying two plates between which the thread is held against friction during its progression from its spool towards the needle. The adjustment of the spring is ensured by means of two levers connecting corresponding points of the spring respectively with the spindle of said arrangement and with the cam normally controlling the actual tensioning of the spring.

United States Patent lnventor Appl. No.

Filed Patented Assignee Priority SYSTEM FOR ADJUSTING THE TENSION OF THE UPPER THREAD IN A SEWING MACHINE 7 Claims, 4 Drawing Figs.

US. Cl

Int. Cl Field of Search 255, 59, 97; 242/150; 226/(no search) 112/254 D05b 47/00 1 l 2/ 254,

[56] References Cited UNITED STATES PATENTS 1,234,322 7/1917 Finch 112/254 1,518,494 12/l924 Elock 112/254 2,609,772 9/1952 Casas-Robert 1 12/254 FOREIGN PATENTS 562,397 8/1958 Canada 112/254 Primary Examiner-Jordan Franklin Assistant Examiner-George H. Krizmanich Att0rneysEmory L. Groff and Emory L. Groff, .lr.

ABSTRACT: A system for adjusting the tensile stress to which the upper thread of the machine is subjected by means of a spring engaging an arrangement including a spindle carrying two plates between which the thread is held against friction during its progression from its spool towards the needle. The adjustment of the spring is ensured by means of two levers connecting corresponding points of the spring respectively with the spindle of said arrangement and with the cam normally controlling the actual tensioning of the spring.

9. 5y I? ,8 I0 I I6 ea 26 K251 2! 14 270 23 PATENTED JAN26 I97!- SHEET 2 OF 2 INVENT OR [Mme/v QAsA5- foatkr ATTORNEY SYSTEM FOR ADJUSTING THE TENSION OF THE UPPER THREAD IN A SEWING MACHINE The present invention has for its object a system for adjusting the tension of the upper thread in a sewing machine, said system including at least two plates fitted on a common spindle and adapted to be urged into contacting relationship over the thread by a spring acting on said plate while a knurled ad justing wheel controls a cam the angular position of which acts on the tension of the spring.

According to the invention, the adjusting system includes a furthermore first lever fitted between the cam and a point of the spring, while a second lever is inserted between a second point of the spring and the spindle over which the superposed plates are to be clamped together.

Such an adjusting system provides a very high accuracy and an extremely fine adjustment of the tension of the upper thread since the adjusting cam acts on the tensioning spring at a theoretically selected point thereof as provided by the presence of the intermediate levers between said cam and the spindle over which the plates are fitted.

The accompanying drawings illustrate diagrammatically and by way of example a preferred embodiment of the tension adjusting system according to the invention. In said drawings:

FIG. 1 is a partly side elevational view and partly a longitudinal cross section of the upper part of the frame of a sewing machine incorporating the tension-adjusting means according to the invention; 7

FIG. 2 is a sectional view through line 11-" of FIG. 1;

FIG. 3 is a view from above the head of the sewing machine;

FIG. 4 is a view from above, partly torn off, of a portion of the head of the sewing machine.

The sewing machine illustrated in the drawings includes a frame 1, the upper surface 2 of which carries the tension-adjusting system generally designated by the reference number 3. Said tension-adjusting system provided for the upper thread 4 of the sewing machine includes two plates 5 fill fitted in superposition round a spindle 6 adapted to slide vertically in a bearing 7 forming part of the frame 1. A blade spring 8 urges the two plates 5 into contacting relationship while a knurled wheel 9 adapted to revolve round a spindle 10 carried by the frame 1 serves as a member controlling the tension-adjusting system. To one side of said knurled wheel 9, there is provided a cam 11 showing a substantially spiral-shaped outline. Said outline of the cam 11 is provided furthermore with notches l2 defining in cooperation with the end 13 of the first lever 14 as many tension-adjusting positions. Said lever 14 is adapted to rock round a pivot 15 rigid with the frame 1 of the sewing machine. For this purpose, the end 16 of the lever 14 facing away from the cam carries two raised lugs 17 through which said lever 14 is pivotally carried by the above-mentioned pivot 15. The spring 8 engages through its outer end 18 the underside of said pivot 15. The other end 19 of the spring 8 is connected through an adjusting screw 20 with an intermediate section 21 of the first-mentioned lever 14. A nut 22 fitted on the screw 20 gauges or adjusts at the start the tension of the spring 8.

A second lever 23 also carries lugs 24 through which it is revolvably secured to the pivot 15 adjacent the lever 14. The free end 25 of said second lever 23 terminates as a fork provided with two tines and engaging a groove 26 formed in the plate-carrying spindle 6. Said second lever 23 includes a transverse section 27 extending laterally underneath the spring 8 and bearing against an intermediate point of the length of said spring 8.

A pin 28 rigid with the frame 1 engages a notch 29 provided in each plate 5 (FIG. 3) so as to prevent said plates 5 from revolving round the spindle 6.

The periphery of the knurled wheel 9 carries a scale 30 whereby it is possible for the sempstress to ascertain, on the outside of the frame 1 the value of the adjustment selected for the tension of the upper thread 4.

In the embodiment illustrated of a sewing machine incorporating a tension-adjusting system, the spool 31 off which the upper thread is unwound is fitted over a spool carrier spindle 32 located in a housing 33 provided in the head of the sewing machine (FIG. 1). Steel spring wires 34 are wound round the spool-carrying spindle 32 so as to hold fast if required the spool 31 with reference to its carrier spindle 32 while a cap 35 rests over the spool 31 so as to guide the thread 4 in its upward direction during its unwinding. The thread 4 passes through the upper surface 2 of the frame 1 as provided by a slot 36 (FIG. 3), beyond which it engages the gap between the plates 5. The thread 4 passing out of said gap engages a thread guide 37 constituted by a bent trough beyond which the thread reaches the front surface of the frame 1 of the sewing machine, on which it engages a further thread guide 38 and a compensating spring 39, the thread engaging then after a thread-drawing lever 40 concealed by a cover 41. The latter is provided with a slot through which the thread issues so as to engage further thread guides 42 and 43 and to finally reach the needle clamping means and the needle eye, which are not illustrated, over the needle bar 44.

The general arrangement of the sewing machine provided with the spool carrier 32 housed within the head of the machine has been described in other patent applications filed by the applicant.

As illustrated in FIG. 3, the upper surface 2 of the frame 1 of the sewing machine carries also a thread guide 45 constituted by a blade projecting above the upper surface 2 of the frame Said thread guide 45 constrains the thread to follow a path extending in the medial plane passing through the cop 51. As illustrated in FIG. 1, said thread guide 45 forms the raised end of a metal strip 46 folded in U-shpae and housed within the frame 1. A screw 47 engages transversely a port 48 formed in the upper surface 2 of the frame and extends freely through one of the arms of the U-sliaped strip 46 so as to be screwed in the opposite arm of the latter. The raised end 49 of the metal strip passes through a slot 50 cut in the frame 1 and forms the thread guide 45. It will be readily ascertained from inspection of the drawings that the fastening or release of the screw 47 urges more or less together the arms of the U-shaped strip 46 whereby the raised'end 49 projects more or less considerably above the upper surface 2 of the frame 1.

In the case where it is desired to prepare a cop 51 over its thread-winding spindle 52 extending above the upper surface 2 of the frame 1, the thread 4 passing off the spool 31 and out of the frame 1 through the slot 36 engages the gap between the plate 5 of the tension-adjusting system 3 exerting a preliminary tensile stress on said thread which engages then after the thread guide 45 before it is wound round the cop 51. Such a special arrangement associated with the tension-adjusting system 3 of the sewing machine provides thus means for wind ing a cop 51 while it is still possible to adjust the tension of the thread 4 passing off the spool 31 towards said cop 51, which adjustment is unfortunately impossible in conventional sewing machines. The tension exerted on the thread 4 during its winding is such that a more uniform winding operation is obtained reliably. v

The sewing machine illustrated by way of example may also be provided on the upper surface 2 of its frame 1 with a second spool-carrying spindle 53 adapted to carry a further spool 54. This allows the cop 51 to be wound with a thread 55 fed by said second spool 54. In such a case, the thread 55 is drawn over the thread guide 45 and engages the gap between the plates 5 of the tension-adjusting system 3, following which the thread 55 is fed again over the thread guide 45 onto the cop 5 1.

It should be remarked that, with such a sewing machine, it is possible to execute seams by means of two upper threads. One of said threads illustrated at 4 is fed by the spool 31 while the other thread 55 is fed by the spool 54. The thread 55 would then pass in the gap between the plates 5 in a direction opposed to that of the passage in the gap of the thread 4 wound off the spool 31. The tension-adjusting system 3 would thus play its part simultaneously for both threads 4 and 55 without any difficulty and without any auxiliary plate being required.

This is ascribable to the fact that the two threads pass through the gap between the plates of the tension-adjusting system in opposite directions while the inlets and outlets provided in the said system for the two threads are out of registry. In order to further such a passage of the two threads in the gap between the plates 5, the latter assume a convex shape in their central area (.FIG. 2). Of course, it is also possible to provide the tension-adjusting system 3 with three superposed plates so as to form a separate channel for each of the two threads 4 and 55. Said two threads 4 and 55 continue progressing towards the needle allotted to them under the guidance of the thread guides 37 and 38, the compensating spring 39, the threaddrawing lever 40 and the thread guides4l2 and 43.

As in all conventional sewn sewing machines, the lever 56 controlling the operation of the presser bar 57 holding the fabric in position serves also, in the case of the machine illustrated, as a member acting through the agency of a connecting rod 58 on the tension-adjusting system 3 in order to obtain the opening of the plates 5 each time the presser bar 57 is raised. To this end the connecting rod 58 is secured through the agency of a pivot 59 to an intermediate point of the lever 656 which is secured to the pivot 60 rigid with the machine frame. The upper end 61 of the connecting rod 58 engages an opening 62 formed in the lever 23 (FIG. 4). A shoulder 63 is provided on the connecting rod 58 so as to raise said lever 23 and therewith the spindle 6 each time the lever 56 controlling the presser bar 57 is raised. It should be remarked that, when said lever 56 is raised, the pivot 59 is shifted towards the opposite side of the geometrical line connecting the shoulder 63 with the pivot 60 which ensures a stable condition on the one hand for the fabric holding the lever 56 in its raised position and on the other hand for the spindle 6 in its plate-releasing position.

The instant arrangement will be more readily appreciated following a brief description of the mechanism controlling the feeding of the upper thread 4 between its spool 34 and towards the machine needle. With the thread 4 sandwiched between the two plated plates 5 it will be understood that the degree of tension applied to the thread will depend upon the amount of downward force exerted upon the vertically slidable spindle 6 about which the plates are joumaled. The free end 25 of the second lever 23 engages the spindle by means of the groove 26 and the lever transverse section 27 provides means by which a controllable downward force may be applied to this second lever to regulate the degree of thread tension'. This force is delivered by means of the spring 8, an intermediate point of which overlies the transverse section 27. Since the outer end 18 of the spring 8 is restrained beneath the pin 15, about which the two levers pivot, it will be seen that manipulation of the other end 119 of the spring 8 will regulate the downward force applied to the second lever 23. This manipulation is provided by the first lever 14 which is connected to the spring 8 by means of the screw attached on the one hand to an intermediate point of the first lever 14 and on the other hand to a point on the spring 8 adjacent its end 19. From the foregoing it will follow that, as the knurled wheel 9 is rotated, its cam 11 will vary the vertical displacement of the first lever 14 and cause a relative vertical displacement of the spring 8 to alter the force being applied to the second lever by means of its transverse section 27 Numerous modifications may be brought to the tension-adjusting system which has just been described.

Thus, the two levers I4 and 23, instead of being set side by side, may be arranged in superposition or possibly they may be pivotally connected each with a different pivot carried by the frame I of the sewing machine. However, it should be remarked that the arrangement disclosed with reference to the accompanying drawings provides a very compact structure of the tension-adjusting system which furthers the assembly of the different components in the upper part of the frame 1 without disturbing by any means the remaining mechanism of the sewing machine. Obviously and in accordance with a modification, the knurled wheel 9, instead of being revolvably carried by a horizontal spindle I0 arallel with the axis of the pivot 18 provided for the levers 4 and 23, may as well be fitted so as to pivot round a vertical spindle in which case the cam Ill forms a bell-shaped cam operating along a vertical component on the end 113 of the lever 14.

I claim:

1. In combination with the body of a sewing machine and the mechanism feeding an upper thread off its spool towards the needle, the provision of a system adjusting the tension of the upper thread and comprising a spindle carried by the frame, at least two thread-tensioning plates carried by the spindle and between which the thread progresses under friction on its path between the spool and the needle, a spring acting on the spindle and plate arrangement, an adjusting knurled wheel revolvably carried by the machine body, a cam controlled by said wheel, a first lever operatively connecting the cam with a first point of the spring, and a second lever engaging a second point on said spring and connecting in turn with said spindle, whereby movement of said cam adjusts in accordance with its angular position the tension exerted by said spring and consequently the tensile stress of the upper thread.

2. A system as claimed in claim 1, wherein the spring is a blade spring, said system comprising a common axis carried by the machine body, and pivotally carrying both the first and the second lever and one end of the blade spring, and an adjustable screw connecting an intermediate point of the first lever with the first point of the spring adjacent the end of the latter.

3. A system as claimed in claim ll, wherein the spring is a blade spring, said spring comprising a common axis carried by the machine body and pivotally carrying both the first and second lever and one end 'of the blade spring, the two levers being set side by side on said axis, and an adjustable screw connecting an intermediate point of the first lever with the first point of the spring adjacent the end of the latter, the second lever including a lateral projection engaging said second point of the spring and the end of said second lever engaging the plate-carrying spindle.

4. A system as claimed in claim I, wherein the spring is a blade spring, said spring comprising a common axis carried by the machine body, and pivotally carrying both the first and second lever and one end of the blade spring, an adjustable screw connecting an intermediate point of the first lever with the first point of the spring adjacent the end of the latter, an auxiliary spindle parallel with said common axis and rigid with the knurled wheel and cam.

5. A system as claimed in claim I, wherein the cam outline is provided with notches adapted to engage selectively the end of the first lever to define corresponding tensile stresses for the spring.

6. A system as claimed in claim 1, wherein the spindle and plate arrangement projects above the body, the system including a cop revolvably carried by the upper surface of said body and thread guide over which the thread passing off the spindle and plate arrangement is fed towards the cop to be wound round the latter under a tension defined by the spindle and plate arrangement.

7. A system as claimed in claim 1, wherein the spindle and plate arrangement projects above the body, the system including an auxiliary thread-carrying spool revolvably carried by the upper surface of said body, thread-guiding means through which the thread passing off the auxiliary spool is fed into the spindle and plate arrangement and between said plates in a direction opposed to that of the progression of the upper thread between said plates and along a path different from that of the upper thread therebetween, and a cop carried by the machine body and round which the thread fed by the auxiliary spool is wound as it passes out of the spindle and plate arrangement. 

1. In combination with the body of a sewing machine and the mechanism feeding an upper thread off its spool towards the needle, the provision of a system adjusting the tension of the upper thread and comprising a spindle carried by the frame, at least two thread-tensioning plates carried by the spindle and between which the thread progresses under friction on its path between the spool and the needle, a spring acting on the spindle and plate arrangement, an adjusting knurled wheel revolvably carried by the machine body, a cam controlled by said wheel, a first lever operatively connecting the cam with a first point of the spring, and a second lever engaging a second point on said spring and connecting in turn with said spindle, whereby movement of said cam adjusts in accordance with its angular position the tension exerted by said spring and consequently the tensile stress of the upper thread.
 2. A system as claimed in claim 1, wherein the spring is a blade spring, said system comprising a common axis carried by the machine body, and pivotally carrying both the first and the second lever and one end of the blade spring, and an adjustable screw connecting an intermediate point of the first lever with the first point of the spring adjacent the end of the latter.
 3. A system as claimed in claim 1, wherein the spring is a blade spring, said spring comprising a common axis carried by the machine body and pivotally carrying both the first and second lever and one end of the blade spring, the two levers being set side by side on said axis, and an adjustable screw connecting an intermediate point of the first lever with the first point of the spring adjacent the end of the latter, the second lever including a lateral projection engaging said second point of the spring and the end of said second lever engaging the plate-carrying spindle.
 4. A system as claimed in claim 1, wherein the spring is a blade spring, said spring comprising a common axis carried by the machine body, and pivotally carrying both the first and second lever and one end of the blade spring, an adjustable screw connecting an intermediate point of the first lever with the first point of the spring adjacent the end of the latter, an auxiliary spindle parallel with said common axis and rigid with the knurled wheel and cam.
 5. A system as claimed in claim 1, wherein the cam outline is provided with notches adapted to engage selectively the end of the first lever to define corresponding tensile stresses for the spring.
 6. A system as claimed in claim 1, wherein the spindle and plate arrangement projects above the body, the system including a cop revolvably carried by the upper surface of said body and thread guide over which the thread passing off the spindle and plate arrangement is fed towards the cop to be wound round the latter under a tension defined by the spindle and plate arrangement.
 7. A system as claimed in claim 1, wherein the spindle and plate arrangement projects above the body, the system including an auxiliary thread-carrying spool revolvably carried by the upper surface of said body, thread-guiding means through which the thread passing off the auxiliary spool is fed into the spindle and plate arrangement and between said plates in a direction opposed to that of the progression of the upper thread between said plates and along a path different from that of the upper thread therebetween, and a cop carried by the machine body and round which the thread fed by the auxiliary spool is wound as it passes out of the spindle and plate arrangement. 